The present application provides a magneto-resistive element excellent in symmetry of playback waveforms. The basic construction of the present application is as follows. That is, a magnetic layer 13, an insulating layer 14, and a magnetic layer 15 are laminated; a power supply 18 for applying a voltage between two magnetic layers is provided; an anti-ferromagnetic layer 16 is laminated on the magnetic layer 15, direction of which magnetization is substantially parallel or counter-parallel with a detecting direction of an external magnetic field, and when the external magnetic field is not present, a power supply 17 for causing a current to flow in a non-magnetic metal layer 12 and in an inner direction of a layer surface thereof is provided so that a direction of magnetization of the magnetic layer 13 is substantially at right angles to the detecting direction of the external magnetic field; and there is provided a signal detector 19 for detecting a change of current tunneling through an insulating layer when the direction of magnetization of the magnetic layer 13 is changed by the external magnetic field.